Short Term/Working Memory

1. Langston, PSY 4040 Cognitive Psychology Notes 4 Short Term/Working Memory

2. What do these have in common? • You can still remember details of your tenth birthday party (which you don’t need), but you have trouble remembering a definition long enough to write it down. • Pizza I: You look up the number of a pizza delivery place and someone asks you a question before you can make the call. When you go to dial, the number is gone. • You’re trying to get the lunch order straight. Three people tell you what they don’t want on their hamburger but you can only remember part of the information. • Pizza II. Why can’t you remember a number and talk to someone, but you can remember a number while you look around the room?

3. What do these have in common? Short-term memory. • Two kinds of memory, short and long. • The duration is short. • The capacity is small. • There are different resources available for different tasks.

4. Architecture Recall our box model: Sensory Store Filter Pattern Recognition Selection STM LTM Input (Environment) Response

5. Short-Term Memory • A brief memory store with a limited capacity that helps you to hold information as you process it.

6. Themes • One STM or many? • Is STM really different from Long-Term Memory? (Later in the class, but the foundation will come tonight.)

7. Two Kinds of Memory • The phenomenological evidence is very strong. Everyone has experienced the phenomenon of having some memories that don’t last long and some that do. What is the evidence for two kinds of memory store?

8. Two Kinds of Memory • Evidence: • The serial position curve. • The task: I present you with a list and you recall it. You can recall the words in any order and try to recall as many as you can (called a free recall task). • We graph the frequency of recall by serial position in the list (first word, second word, etc.). • Looking at that curve can tell us something about memory stores.

9. Two Kinds of Memory • Here are classic serial position curves (Deese & Kaufman, 1957): 10 item list 32 item list Deese & Kaufman (1957, p. 182)

10. Two Kinds of Memory • It also works for the position in a passage from the World Almanac (Deese & Kaufman, 1957): Passages Deese & Kaufman (1957, p. 182)

11. Two Kinds of Memory • There are two parts to the curve. The first part is called primacy (it’s the earlier words) and the last part is called recency (it’s the most recent words).

12. Two Kinds of Memory • Our curves again (Deese & Kaufman, 1957): Primacy Deese & Kaufman (1957, p. 182)

13. Two Kinds of Memory • Our curves again (Deese & Kaufman, 1957): Recency Deese & Kaufman (1957, p. 182)

14. Two Kinds of Memory • People start by writing down the last words they heard. Recency is high because people just dump out the contents of STM.

15. Two Kinds of Memory • You can see that here in the order of recall(Deese & Kaufman, 1957): Last part recalled first Deese & Kaufman (1957, p. 182)

16. Two Kinds of Memory • When people go back to words they have to try to remember, they produce the recalls that will go into the primacy part. This part is coming from LTM.

17. Two Kinds of Memory • Try the free recall demonstration here…

18. Two Kinds of Memory • Glanzer and Cunitz (1966): • Even though it looks like one curve, it actually reflects two kinds of memory.

19. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can test this by thinking of variables that should affect each kind of memory differently. • What should affect recency(STM) but not primacy(LTM)? • Whether or not people can recall right away. If STM doesn’t last long then having to wait will allow it to go away and there won’t be anything for recency. Since you wait for primacy anyway, it won’t matter. • G&C: Make people count backwards before they get to recall.

20. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of counting backwards: No counting, standard serial position effect. Glanzer & Cunitz (1966, p. 358)

21. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of counting backwards: 10 seconds of counting, recency way down. Glanzer & Cunitz (1966, p. 358)

22. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of counting backwards: 30 seconds of counting, recency gone. Glanzer & Cunitz (1966, p. 358)

23. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of counting backwards: Note: You still get primacy no matter the delay. Glanzer & Cunitz (1966, p. 358)

24. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can test the two store explanation of the curve by thinking of variables that should affect each kind of memory differently. • What should affect primacy(LTM) but not recency(STM)? • How much time people have between each item. With more time, there’s more time to rehearse, and more stuff should get into LTM. Since recency isn’t based on how much you rehearse, it shouldn’t be affected. • G&C: Space out the words in the list.

25. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of spacing: 3 seconds, low primacy Glanzer & Cunitz (1966, p. 354)

26. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of spacing: 6 seconds, medium primacy Glanzer & Cunitz (1966, p. 354)

27. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of spacing: 9 seconds, higher primacy Glanzer & Cunitz (1966, p. 354)

28. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of spacing: Note: You still get recency, and they’re all about the same. Glanzer & Cunitz (1966, p. 354)

29. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can test the two store explanation of the curve by thinking of variables that should affect each kind of memory differently. • What else should affect primacy(LTM) but not recency(STM)? • How many times people see each item. With more presentations, there’s more time to rehearse, and more stuff should get into LTM. Since recency isn’t based on how much you rehearse, it shouldn’t be affected. • G&C: Present the words more than once.

30. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of presentations: Once, lower primacy Glanzer & Cunitz (1966, p. 354)

31. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of presentations: Twice or three times, higher primacy Glanzer & Cunitz (1966, p. 354)

32. Two Kinds of Memory • Glanzer and Cunitz cont’d.: • We can see the effect of presentations: Note: Recency not affected here either. Glanzer & Cunitz (1966, p. 354)

33. Two Kinds of Memory • Research like Glanzer and Cunitz (1966) also represents an important tool in cognitive psychology called the double dissociation. • The basic idea is that if different parts of a task use different processes, then different variables will affect those parts differently.

34. Two parts of the curve (two kinds of memory): Two Kinds of Memory • This makes it more clear:

35. Two Kinds of Memory Two task parameters:

36. Two Kinds of Memory Expected patterns (in green): • This makes it more clear:

37. Two Kinds of Memory Expected patterns (in green): • This makes it more clear:

38. Since the patterns are different, it suggests the two kinds of memory are independent. Two Kinds of Memory • This makes it more clear:

39. Two Kinds of Memory • Also neuropsychological evidence: • HM: Damage to hippocampus when having corpus collosum severed. Could remember old stuff, but could not acquire new memories. Appeared to have STM deficit and transfer deficit (anterograde amnesia). • Also people with retrograde amnesia who can learn new things but forget parts of their past. • Suggests another type of double dissociation.

40. Connection • We can address our first question: • You can still remember details of your tenth birthday party (which you don’t need), but you have trouble remembering a definition long enough to write it down. • Why?

41. Properties of STM • Now that we have decided that STM and LTM are separate, what are the properties of STM? • Duration. • Capacity. • Mechanism of forgetting. • Representation (code). • Search.

42. Properties of STM • Duration: • Peterson and Peterson (1959) had people learn a list of three letters, count backwards, and recall it. • The counting could go from 0 to 18 seconds. • What they found was that after 18 seconds, STM recall was virtually zero. • This was the inspiration for Glanzer and Cunitz’s (1966) counting backwards task. • Look at the data graph…

43. Properties of STM • Duration: Peterson & Peterson (1959, p. 195)

44. Connection • Duration: • We can answer Pizza I: • Pizza I: You look up the number of a pizza delivery place and someone asks you a question before you can make the call. When you go to dial, the number is gone. • Why?

45. Properties of STM • Capacity: • Measured using span tasks. • I present you a list of information (e.g., s, r, d, g, n, v, p), and you repeat it back. • We make the lists longer until you can’t do it.

46. Properties of STM • Capacity: • Miller (1956) noted that over a variety of span tasks (letters, digits, words, binary numbers…) people came out with a capacity of 7 plus or minus 2. That’s the capacity (since the task is clearly using STM).

47. Properties of STM Miller (1990, p. 349; from Hayes, 1952)

48. Properties of STM • Capacity: • As Miller (1990) puts it: “Absolute judgment is limited by the amount of information. Immediate memory is limited by the number of items.” (p. 349) • We did a span task in CogLab, we can look at the results…

49. Properties of STM • Capacity: • Note that a process called chunking messes up our measure of span. • A chunk is an integrated unit of information. You could remember seven digits, or you could call it “my phone number” and then it’s just one thing. • The capacity is really 7 plus or minus 2 chunks.

50. Properties of STM • Capacity: • Consider this from Miller (1990): Miller (1990, p. 350)